The present invention relates to a device for engaging and disengaging blanket cylinders of a four-cylinder printing mechanism for a roller rotary offset printing machine in which all four cylinders are positioned obliquely to the direction of running path and one above another; central axes of the cylinders lie approximately on the straight line.
Printing assemblies of the type under discussion have been known, which have been provided with switch-on and off devices for blanket cylinders of the roller rotary offset printing machine. Such a device has been disclosed, for example in German patent DE-PS 34 12 812. Four cylinders in this known assembly are arranged one above another along the straight line which is inclined relative to the horizontally extending path of running of the machine, and the pins of the blanket cylinders are each positioned in two eccentric sleeves arranged one inside the other in a bore of the wall of the printing mechanism. These two sleeves are arranged in that bore with the same eccentricity. The inner and outer eccentric sleeves are connected to each other by a common pulling rod and are adjustable, via another pulling rod, by means of an adjusting device in such a fashion that the blanket cylinders move in opposite directions by angle 90.degree. relative to the inclined straight line linearly, whereby the central axes of the pins of the blanket cylinders are positioned at the different sides of the straight line and spaced from said straight line at the smallest intervals.
This known device has the disadvantage which resides in that due to the linear movement to the right relative to the straight line connecting the central axes of the plate cylinders, the infeed between the blanket or internal cylinders almost doubles as compared to the infeed between the respective blanket cylinder and respective plate cylinders which results in respectively different adjustment forces. Due to wear, the adjustment forces between the pairs of the cylinders of the printing assembly should be changed, and therefore in each pair the cylinders must be connected to each other and disconnected from each other individually. Many required adjustment structural components provided for this purpose thus lead to considerable expenses.
The printing assembly of the type under discussion has been disclosed also, for example in applicant's U.S. Pat. No. 4,183,297 the disclosure of which is incorporated herein by reference.